(Make sure to strain turkey drippings first to get rid of any large chunks before using)
Place strained turkey drippings in a large saucepan. Let it sit for 5 minutes, then skim any fat from the top surface. Add butter to drippings then cook over medium-high heat. Bring to a simmer and cook for 15 minutes, stirring often, until slightly thickened.
Mix together cornstarch and water to create a slurry. Whisk slurry into the saucepan. Then whisk in gravy packet contents, if using. Continue to simmer until gravy thickens. Season with salt and pepper, if needed.
Serve warm and enjoy!